An organic electronic device means a device that requires exchanging of electric charges between electrodes using holes and/or electrons and organic materials. The organic electronic device may be largely divided into the following categories according to an operation principle. First, there is an electronic device in which an exciton is formed in an organic layer by a photon that flows from an external light source to the device, the exciton is separated into electrons and holes, and the electrons and the holes are transferred to the other electrodes and used as a current source (voltage source). Second, there is an electronic device in which holes and/or electrons are injected into an organic material semiconductor forming an interface in respects to the electrode by applying a voltage or a current to two or more electrodes, and the device is operated by the injected electrons and holes.
As examples of the organic electronic device, there are an organic light emitting device, an organic solar cell, an organic photoconductor (OPC), an organic transistor and the like, and all of them require a hole injection or transport material, an electron injection or transport material or a light emitting material in order to drive the device.
Hereinafter, an organic light emitting device will be mainly described in detail. However, in the organic electronic devices, all of the hole injection or transport material, an electron injection or transport material or a light emitting material are operated on the basis of the similar principle.
In general, an organic light emitting phenomenon means a phenomenon that converts electric energy into light energy by using an organic material. The organic light emitting device using the organic light emitting phenomenon has a structure which generally comprises an anode, a cathode, and an organic layer that is disposed between them. Herein, most organic layers have a multilayered structure that comprises different materials in order to increase efficiency and stability of the organic light emitting device, and for example, it may comprise a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer and the like. In the organic light emitting device structure, if a voltage is applied between two electrodes, holes are injected from an anode and electrons are injected from a cathode to the organic material layer, and when the injected holes and the electrons meet each other, an exciton is formed, and light is emitted when the exciton falls to a bottom state. It is known that this organic light emitting device has properties such as magnetic light emission, high brightness, high efficiency, low driving voltage, a wide viewing angle, high contrast, high speed response and the like.
In the organic light emitting device, the material that is used in the organic material layer may be classified into a light emitting material and an electric charge material, for example, a hole injection material, a hole transport material, an electron transport material, an electron injection material according to a function thereof. The light emitting material may be classified into a high molecule type and a low molecule type according to the molecular weight, and a fluorescent material and a phosphorescent material according to a mechanism of light emission. In addition, the light emitting material may be classified into blue, green, and red light emitting materials and yellow and orange light emitting materials in order to realize better natural colors according to the emission color.
Meanwhile, in the case of when only one material is used as a light emitting material, by interaction between molecules, there are problems in that the maximum light emitting wavelength moves to the long wavelength, the color purity is lowered, or efficiency of the device is lowered because of reduced effect of light emission. Therefore, in order to increase color purity and increase emission efficiency through transferring of energy, a host/dopant system may be used as the light emitting material. The principle is that if a small amount of dopant that has a smaller energy band gap than a host forming the light emitting layer is mixed with the light emitting layer, the exciton that is generated from the light emitting layer is transported to the dopant to emit light at high efficiency. At this time, since the wavelength of the host is moved to the wavelength bandwidth of the dopant, a desired wavelength of light may be obtained according to the kind of dopant.
In order to sufficiently show excellent properties of the above organic light emitting device, a material constituting the organic material layer in the device, for example, the hole injection material, the hole transport material, the light emitting material, the electron transport material, the electron injection material and the like should be supported by stable and efficient materials. However, the development of a stable and efficient organic material layer material for organic light emitting devices has not yet been made. Therefore, there is a demand for developing a novel material, and the demand for developing the novel material is similarly applied to the other organic electronic device.